Blast furnace



Apri] 10, 19.45. Y 1 s, STEWART 2,373,514

BLAST FURNACE Filed March 17, 1943 2 Sheets-Sheet l Y l l H 'fr//////////// April 10 1945- J. s. STEWART 2,373,514

BLAST FURNACE Filed March 17. 1945 2 Sheets-Sheet 2 fr I',

rumn. Atother localities in 'Patented Apr; 1o, 1945 UNITED STATES`PATENT 0F FICE BLAST FURNACE J ohh S. Stewart, New York, N. Y.

Application March 1 7, 1943, Serial No. 479,501 11 Claims. (Cl. 26d-25)This invention relates to blast furnaces of the general type comprisinga Vertical stack or shaft adapted to contain the charge of material-ore,

sinter or scrapto be smelted and which latter in conventional toconstrict the furnace in the vicinity of the tuyre plane-i. e., thehorizontal plane intersecting the discharge nozzles of the tuyres. Thatis, th'e furnace above the tuyres is usually expanded upwardly andoutwardly forming what is known as a "bosh, and aoften this taper iscarried all the way up to the ^charging floor at the top of the stack.

Such furnaces, because of' their upwardly expanding diameter, aresubject to the disadvantage that the descent of the charge in the stackis slowed down andthe velocity and pressure of the ascending combustionvgases are likewise retarded. Furthermore, the bosh because of suchair-permeability with a consequent diminution of the air supply.

Under such conditions, the chargelsubsides very.

slowly and, because of its longer exposure to the hot .ascendingcombustion gases, the srnelting zone rises higher and higher in thestack, producing what is known as hot tops. Such hot .tops resultA inunsatisfactory furnace performance as evidenced by reduced output, lossof metal by volatilization, and additional metal losses in the` coldslags accompanying such. faulty operation. Y It is an important objectof the present invention to provide a blast furnace of the above typewhich is so constructed and arranged as to overtaper, denes skewbacksupon the baseoi' the stack against which the charge in its semi-fusedstate can lodge, eventually forming an arch overlying thesmelting zoneand blocking the stack passageway.

It is well known that after a furnace has beenin operation for a shorttime. accretions .begin to collect on the bosh, these secretions formingshelves upon which additional deposits continue to build,.and graduallyincrease in' thickness and height. Y Finally there remains'only arestricted j openingnear thecenter -of the column of charge l in thenature of afcrack of varying width extending from the tuyreI planeupwardly to the tcp of the charge column. Subsequently, at some place orplaces in the furnace this crack bridges over so as to form an archoverlying the smelt-` ing zone. Such an arch. besides-preventing thefree descent of the charge in the stack, interferes with the uniform andequal distributional the A hot combustion gases therethrough, with theresult that eventually a portion of the 4iurnacef'goes "dead" and ceasesto smelt.- Under thesedead vspots air pockets fed from several tuyresmay form and -develop ruptures,

known as biow holes, extending to thetop of` the charge co1- the furnacethe charge choked with nne'ore or other mawith secretions so that itloses its may become terlnl and come the foregoing disadvantages. Moreparticularly, this object is attained by providing t-he furnace at thelower end of the stack with an enlarged smelting chamber, the transversecrosssectional area, of which on the tuyre planer is appreciably greaterthan the corresponding .area for any horizontal plane intersecting thestackthis being the reverse of usual blast furnace. delsign in which thestack ordinarily increases in width above the tuyre plane to form thebosh.'

Another object of the invention is to provide a blast furnace of theabove character so con-1 structed and arranged as to accelerate thedownward movement of the furnace charge through the stack, and moreespecially to prevent'.the charge from bridging over the smelting zonewith the consequences previously explained.

Another object of the'invention is to provide a blast furnace of theabove character having an enlarged smelting chamber and means fordischarging a large volume of air therein for effecting the intense and'rapid s melting of the furnace charge; and thus increasing'the operating capacity of the furnace.

Still anothfer object ofthe invention is to provide a blast furnace ofthe above character including means for increasing the blast pressure inthe stack in order to blow out the ore particles or lines whichotherwise would accumulate on the wall o f the stack.

The invention has a further object to provide Va blast furnace of theabovelcharacter in which the tuyres are so .located with respectto thesmelting chamber as to insure that the smelting zone is conned entirelywithin the chamber without extending up into the smallerarea'ot the.stam e e "ce Y Providing s blast fum lenerally er :ne form er mmvemdflmnel. the upwardly sus mmm, an,...

tion of which defines the smelting chamber and the upright tubularportion, the stack. The wall of the smelting chamber preferably isinclined at an angle somewhat greater than the angle of repose of thefurnace charge sovas to insure close confinement of the charge withinthe chamber.

' By reason of the greater value of the smelting chamber relative to thestack per unit of height,

vand because of the larger'smelting zone thereby provided, thesubsidence of the charge within the l0 shaft takes place more rapidlythan in blast; fur-l naces of conventional boshed design. As a rel sult,there is less opportunity for the combustion zone to rise within theshaft, causing hot topsv and loss ofmetal by volatilization, whichfurther resultsdn cold slags. Also, because the staclr` is smaller intransverse cross-section than that of the sm'elting chamber, a strongerflow of combustion gases will be forced up the stack to carry off theilnes that tend to collect on the wall of the stack and clog thepassageway.

Other objects and advantages will be apparent from the followingdetailed description of a' preferred embodiment of the invention,vreference being. had to the annexed drawings, in which:

Figure 1 shows in vertical cross-section a schematic view of a blastfurnace of a type suitable for the reduction of sintered lead sulphideores and other lead-bearing materials;

Figure 2 is an enlarged vertical cross-,sectional view through `thesmelting chamber ofthey furnace of Fig. l;

' Figure 3 is a plan of the furnace; and

Figure 4 is a transverse cross-sectional View taken on the tuyreplanelthrough a blast furnace of modied shape.

The blast furnace schematically shown in the drawings comprisesgenerally a smelting chamber I, an upright stack 2 rising centrally"from the top of the smelting chamber and having its upper `endcommunicating through a ring 3 located in the charging floor 4 with aconical hood 5. The

hood 5 leads upwardly into a chimney 6 venting to the atmosphere. Achute I extends downwardly at an angle, passing through the hood, forfeeding charges of material to be smelted into the yfurnace from a binor charge skip, the discharge maintaining combustion to eiect thesmelt-ing of the ore, air blasts are directed into the smelt-` ingchamber and into the body of the-charge occupying the chamber from aseries of tuyres 9 leading oil' from a bustle pipe I0 encirclingthefurnace and connected at IIla with'a source of air under pressure. lf V v The stackand smelting chamber may be of any suitable shape intransverse cross-section, but ordinarily will be circular, as indicatedin Fig. 3'. 'I'he walls of the stack and the smelting chambercuredtogether side-byf-side (Fig. 3) and forming to prevent theirburning out. The furnace' rests upon a hearth IIv forming ashallowcrucible -I2 fromwhlch molten metal ls removed through a.

welll-'|3. For drawing off slag, a tap I4 is provided through the `wallof thesmelting chamber above the hearth level.

.acumenl conduit I s leads oir` nomme chimney 6 and opens into the topof`a, cyclone type of dust-separator I6. A conduit I`I extends from thetop of the separator to a bag house (not shown). Within thebranchconnection I5, and also within the chimney 6 above the point Aofconnection of the branch therewith, are wing dampers I8 and Isa,respectively, which may be so adjusted as to routeA the furnace gaseseither directly up the chimney to the atmosphere (as will be the casewhen starting up vthe furnace) or through the separator I6. and flnescarried over from the furnace in the combustion gases and 'the separatedmaterial spilling from the lower.end of the separator may be collectedin carsV I9 or in any other suitable receptacle. The ilnes may thenbesintered or agglomerated in any well-known manner and returned to thefurnace.

`The smelting chamber'tapers upwardly and inwardly from the hearth at anangle of approximately 65 degrees to the point of itsilunction with thebase of the stack. The enlarged smelting chamber thus provided affordsspace for accommodating a large quantity of coke. Likewise theincreasedl diameter 4 of the smelting chamber allows more tuyres 9 to bearranged about its circumference with their discharge nozzles openinginto the chamber on the tuyre plane 3-3 for supplying an abundance of4air to the coke. This results in creating a large, intensely hotsmelting zone S within the vor-e lbody filling the smeltng chamber.

The number of tuyres 94 will be determined largely by the size of thefurnace which in turn governs the sizeof its smelting zone. lMost of thetuyres are set at right angles to the wall of the smeltingjchamber so astodirect their air blasts of the height of the chamberin order .thatthev smelting zone S produced by the -air blasts'is maintained near thebottom of the chamber and sulciently far below the base of the stack toprevent it from creeping up into the stack during the operation of thefurnace.

By manning the wan `of the smelunjg chamber at an angle of approximately65 degrees, -which is slightly more than the angle'of repose'ofthefurnace charge, the entire space of the chamber is kept filled with thecharge and this condition is further aided by 4thefweight of the charge.may be composed of hollow metalsections la se- "jackets through whichcooling water is circulated column inthe stack. Such an angle alsolendsproperproportion to the furnace when the furnace is designed withsuitable regardI to the `volumetric relationship-between the smeltingchamber and-.the stack. That is, for assuring the descent of the chargethrough the stack atr the lmost ei'licient rate of travel, `the ratiobetween the volume o f that part of the smelting chamber includedbetweenthe tuyre plane," and` the base` 'of the stack 'and the volume oflt'he stack fora corresponding 4rise yin height, should beapproximatelyF 231,321.00. Likewise thef'vertical distance between thetuyre plane and the base of the stack, as compared with' the "diameterof the stack, should bear a relationship of about l.00:0.78.Tl'ie'selratios are approximate for blast `Vfurnaces of circulartransverse.cross-section and are subjectto variation within reasonablelimits.

The. separator removes the dust asvalsiiV reason that it xes thelocation of the smeltingv zone far enough below the base of the stack toavoid the extension of this zone. during the operation of the furnace,up into the stack.

In the form of blast furnace just described the increased size of thesmelting chamber provides for contact of a large volume of coke with alarge v'olume of combustion air so as to produce a large,high-temperature zone of combustion. This results in a high COconcentration, rapid smelting and 'relatively low metal losses in theslag. Also the enlarged smelting chamber, because it provides for'agreater amount of furnace charge per unit of jacket surface incomparison with present blast furnaces, results in more economicaloper,- ation due to less heat dissipation and hence lower cokeconsumption. The increased hearth area permits a larger storage-of slag,and hence allows a longer interval between successive slag tappings,which makes for `a better settling of the slag, allows more time for'the reduction of the metal compounds therein, and leads to more uniformtemperature conditions within the furnace. Because of the difference incross-sectional area of the stack and smelting chamber, the

charge will descend rapidly in the stack and spread out in thin layersin the smelting chamber, thus assuring a better and 'more intimatemixture` of the charge. As a' result of the faster descent of the chargethroughthe shaft, the shaft may be made shorter in length than in blastfurnaces built according to present practice.

An advantage which follows from having the tuyres 9 enter the smeltingchamber through its upwardly and inwardly inclined Wall, preferablyapproximately perpendicular thereto, is that this overcomes to a largelextent the tendency to 'clogging of the tuyeres. Heretofore, intheusual bosh which inclined upwardly and outwardly,

' considerable diculty was encountered in maintaining the tuyeres openbecause ofthe flow of the slag on the wall o-f the smelting chamberdownwardly into the open ends of the tuyres. By reason of theoverhanging wall of the 'smelting chamber in my furnace, the slag cannotdrop into or build u'p aroundthe nozzles of the tuyres. The air injectedthrough the tuyres is under suicient pressure to force its way Well intothe bottom of the column of charge', thereby causing intensivecombustion of the coke and rapid oxidation of the sulphides. Thisgenerates a high tem perature within the charge which rapidly melts theore and creates a large percentage of CQ forthe reduction of the oxides.

Due to the increased number of tuyres, a large volume of air is fed tothe smelting chamber, and consequently a large reduction zone is createdWithin-the-body of the furnace charge. And because this relatively largevolume of air must escape through the stack of small cross-sectionalarea a strong draft will be createdy upwardly through the charge fillingthe stack so as to carry V off the fines that otherwise would tend toclog the passageway or build up as accretions on the stack wall. Thesefines, as' has already been explained,

- are recovered in the separator I6.

Other advantagesof vthe blast furnace just described are as follows:

The smaller area of the shaft compared with shafts f present blastfurnaces of the same capacity allows a simpler mode of charging, doingaway with spreaders, expensive charge cars, etc., and permits the use ofa simpler and cheaper .The furnace need'not be circular in shape. In

Fig. 4 isI disclosed a cross-sectional view of a fur I nace of modifiedform taken on the tuyre plane through its smelting chamber. As indicatedin this figure the contour of the smelting chamber is that of aflattened oval as is also. that of the stack 2', indicated in phantomoutline. In 'this form of the furnace the same general relationshipshold true; that is, the wall of the smelting chamber tapers upwardly andinwardly from the hearth to the base of the stack to provide for anenlarged smelting zone, and the plane of the tuyres 9 is located notsubstantially more than to 30% of the height of the chamber in order toconfine the smelting zone entirely within the chamber. Manifestly thefurnace maybe of rectangular or any other shape in cross-section as maybe found most satisfactory or desirable.

I am aware that it has heretofore been proposed to provide furnaces withan enlarged hearth area, asexemplied by the heap furnace disclosed inthe early patent to C. W. Munson, No. 983,833. Such furnaces, however,are not intended for nor are they capable of carrying out 'blast furnaceoperations. I am also aware that it has been proposed to design blastfurnaces so that their circumferences gradually taper lupwardly andinlwardly throughout the major portion -of their length, but in suchfurnaces the angle of taper is insufscienf, to matriany affect the rateof suby sidence of the furnace charge or the flow of the .current ofcombustion gases through the stack, and these furnaces otherwise fail toaccomplish the many objects I have above explained.

Manifestly various changes in structure-and design may be made in theform of smelting `furnace described above, which is to be regarded asexemplary and not restrictive of the invention, without departing fromthe spirit of my invention as defined by the following claims.

rI claim:

1. A blast furnace comprising a smelting chamber, a vertical shaft'extending upwardly from said chamber, said shaft and chamber beingadapted to receive and conne a charge of material to be smelted, anopening for charging material into the top of said shaft tosubstantially ll the shaft and chamber, a series of tuyres dischargingthrough the wall of the chamber in a tuyre plane located sufficientlybelow the base of the stack as to'avoid extension of the smelting zonefrom the chamber into the stack, and means for withdrawing slag andmolten metal from the,

bottom of said chamber, said chamber having its wall tapered upwardlyand inwardly between the tuyre plane and the base of the stack at an`inclination such as to embrace and confine the said chamber, said shaftand chamber being rial to be smelted, an opening for charging materialinto the top of said shaft to substantially ll the shaft and chamber, aseries of tuyresdischarging through the wall of the chamber in a tuyreplane located sufliciently below the base of the stack as to avoidextension of the smelting zone from the chamber into the stack, andahearth providing a crucible for receiving molten metal at the bottom ofsaid chamber, said chamber having its wall tapered inwardly and up-4adapted to receive and confine a charge of matewardly at an angle notsubstantially less than 65 degrees to the horizontal so as to providespace to accommodate an enlarged smelting zone.

3. A blast furnace comprising a smelting chamber, a vertical shaftextending upwardly from said chamber, said shaft and chamber being ,4adapted to receiv'jand confine a charge of vmaterial. to be smelted,"anopening for charging material into the top ofsaid shaft to substantiallyfill the shaft and chamber, a series of tuyres discharging through theWall of the chamber in a tuyre plane located suiiciently below the baseof the stack as to avoid extension of the smelting zone from the chamberinto the stack, and a *I hearth providing a. crucible for receivingmolten metal at the bottom of said chamber, said chamber having its walltapered upwardly and inwardly from the hearth to the base of the stack,

and said tuyre plane being located not substantially above percent ofthe vertical height of said, chamber. l

4. A blast furnace comprising a smelting Y chamber, a Vertical shaftextending upwardly from said chamber, said shaft and chamber beingadapted to receive and connea charge of material to be smelted, anopening for charging material into the top of said shaft to substan'-tially' fill., the shaft and chamber, a series of tuyres dischargingthrough the wall of the chamber in a tuyre plane located suicientlybelow the base of the stack as to avoid extension of the smelting zonefrom 'the chamber into the stack, and a hearth providing a crucible` forsaid chamber, said shaft and chamber being of circular transversecross-section and adapted to receive and confine a. charge of materialto be smelted, an opening for charging material into the top of the,stack to substantially ll the shaft chambena vertical shaft extendingupwardly from said chamber, said shaft and chamber being of circulartransverse cross-section and adapted to receive and' confine a charge ofmaterial to be smelted, an opening for charging' material into the top'of the stack to substantially flll the shaft and chamber, a series oftuyres discharging through the wall of the chamber in a tuyre planelocated a substantial distance below the bottom of the stack so as toavoid extension of the smelting zone from the chamber into the stack,said tuyres being directed downwardly toward the hearth of the furnace,and a hearth providing a crucible for receiving molten metal at thebottom of said chamber, said chamber `having its wall tapered `,upwardlyand inwardly between the hearth and the stack and the ratio of thevolume ,of the chamber between the tuyre plane and the stack to thevolume of` thestack for an equal rise in height being not substantiallyless than 2.73:l.00.

'7. A blast furnace comprising asmelting chamber, a vertical shaftextending upwardly from. said chamber, said shaft and chamber being oflcircular transverse cross-section and adapted to 1 receive and conne acharge of material to be smelted, an opening for charging material intothe topl of the stack to substantially ll the shaft.

and chamber, a series of tuyres discharging through the Wall of thechamber in a tuyre plane located a substantial distance below the bottomof the stack so as to avoid extension of the smelting zone from thechamber into the stack, said tuyres being directed downwardly toward thehearth of the furnace, and a hearth providinga crucible for receivingmolten metal at `the bottom of said member, said chamber having its walltapered upwardly and inwardly between the hearth and the stack at anangle not substantially less than degrees to the horizontal and theratio of the volume of the chamber between the tuyre plane and the stackto the `volume of the stack for an equal rise in height being notsubstantially less than 2.73:1.00, and

the tuyre plane being located not substantially above one-quarter of thevertical height of said chamber.

8. A blast furnace comprising a smelting chamber,a vertical shaftextending `upwardly from said chamber, said shaft and chamber being ofcircular transverse cross-section and adapted to receive and confine acharge of material to bel smelted, an opening for charging material intothe top of the stack to substantially ll the shaft and chamber, a seriesof tuyres discharging v through the wall of the chamber in a tuyre planeand chamber, a. series of tuyres discharging I through the wall of the'chamber in a tuyre plane located a substantial distance below thebottom of the stack so as to avoid extension of the smelting zone fromthe chamber .into the stack, said tuyres being directed downwardlytoward the hearth of the furnace, and a. hearth providing a,

crucible for receiving molten metal at the bottom of said chamber, saidchamber having its wall tapered," upwardly and inwardly between thetuyre plane and the stack at an angle not less than the angle of reposeofthe material so as to Provide space to accommodate an enlargedsmelting zone; f

6. A blast furnace comprising a smelting located 'a substantial distancebelow the bottom of the stack so as to avoid extension of the smeltingzone from the chamber into the stack, said tuyres being directeddownwardly toward the hearth of the furnace, and a hearth providing acrucible for receiving molten metal at the bottom of said chamber, saidchamber having its wall tapered upwardly and inward-ly between thehearth and the stack and the ratio of the vertical distance between thetuyre plane and the base of the stack and the diameter of the stackbeing not substantially less than 1.00:0.'78. 1 ,l

9. A blast'furnace comprising a smeltng chamber,` a vertical shaftextending upwardly from said chamber, said shaft and chamber being ofcircular transverse cross-section and adapted to receive and conne acharge of material to be smelted, an opening for charging material intothe top of the stack to substantiany nuv the shaft and chamber, a seriesof tuyres discharging through the wall of the chamber in a tuyre planelocated a substantial distance below the bottom of the stack so as toavoid extension of the smelting zone from the chamber into the stack.said tuyres being directed downwardly toward the hearth of the furnace,and a hearth providing a crucible for receiving molten metal at Ythebottom of said chamber, said ,chamber having its walltapered upwardlyand inwardly between the hearth and the stack at an angle not 'fsubstantially less than 65 degrees to the horizontal and the ratio ofthe vertical distance between the tuyre plane and the base ofthe stackand the diameter of the stack being not substantially less than1.00:0.78.

. 10. A process of smelting which comprises conbase portion and a highgas pressure -area at and below the junction of the column with the baseand overlying the smelting zone, whereby to increase the pressure andtemperature in the smelting zone so as to give maximum concentration ofcarbon monoxide in the gases when the charge of carbonaceous material,carbon dioxide and carbon monoxide are in equilibrium` within thesmelting zone, and to increase the temperature of the slag.

11. A process of smelting which comprises confining the charge withinthe walls of a blast flning in a closed chamber the charge to be smeltedin the form of an inverted funnel so as to define a base portion in theshape of a truncated cone and a vertical column oi' restricted diameterextending upwardly from the base portion, the walls of the confiningchamber completely conning and lying substantially in contact with thebody of charge without intervening spaces, said charge comprising ametal-bearing material, a iluxing material and a solid' carbonaceous ffuel, injecting a large volume of air into the base portionadjacent itsbottom at -a multiplicity of circumferentially-spaced points so as toproduce a smelting zone located wholly within the furnace in the form ofa vertical column terminating in an enlarged :base having downwardly andoutwardly sloping sides completely confined by and wholly lying in closecontact with the celerate the descent of the charge through the columnand to increase the pressure of combustion gases within the base.

CERTFICATE 0F CORRECTION`.

rasant Nc,- 2,375,511.

It is hereby certified that error appearsv inthe printed specificationof the above numbered patent requiring correction as follows: Page 2,first column, line 7, for the.wrd'va1ue" read -1--vo1u1ne, 'andthat theVsaid Letters Patent should be read withl this correction thereintha'tthe same JOHN s. STEWART'.

may conform to( the record ofthe 'case in theI Patent Office.- 'Signedand ysealed this 26th day of June, A. `D. 1914.5.

i (Seal)v Leslie Frazer y Acting commissioner' of Patents.

and chamber, a series of tuyres discharging through the wall of thechamber in a tuyre plane located a substantial distance below the bottomof the stack so as to avoid extension of the smelting zone from thechamber into the stack. said tuyres being directed downwardly toward thehearth of the furnace, and a hearth providing a crucible for receivingmolten metal at Ythe bottom of said chamber, said ,chamber having itswalltapered upwardly and inwardly between the hearth and the stack at anangle not 'f substantially less than 65 degrees to the horizontal andthe ratio of the vertical distance between the tuyre plane and the baseofthe stack and the diameter of the stack being not substantially lessthan 1.00:0.78.

. 10. A process of smelting which comprises conbase portion and a highgas pressure -area at and below the junction of the column with the baseand overlying the smelting zone, whereby to increase the pressure andtemperature in the smelting zone so as to give maximum concentration ofcarbon monoxide in the gases when the charge of carbonaceous material,carbon dioxide and carbon monoxide are in equilibrium` within thesmelting zone, and to increase the temperature of the slag.

11. A process of smelting which comprises confining the charge withinthe walls of a blast flning in a closed chamber the charge to be smeltedin the form of an inverted funnel so as to define a base portion in theshape of a truncated cone and a vertical column oi' restricted diameterextending upwardly from the base portion, the walls of the confiningchamber completely conning and lying substantially in contact with thebody of charge without intervening spaces, said charge comprising ametal-bearing material, a iluxing material and a solid' carbonaceous ffuel, injecting a large volume of air into the base portionadjacent itsbottom at -a multiplicity of circumferentially-spaced points so as toproduce a smelting zone located wholly within the furnace in the form ofa vertical column terminating in an enlarged :base having downwardly andoutwardly sloping sides completely confined by and wholly lying in closecontact with the celerate the descent of the charge through the columnand to increase the pressure of combustion gases within the base.

CERTFICATE 0F CORRECTION`.

rasant Nc,- 2,375,511.

It is hereby certified that error appearsv inthe printed specificationof the above numbered patent requiring correction as follows: Page 2,first column, line 7, for the.wrd'va1ue" read -1--vo1u1ne, 'andthat theVsaid Letters Patent should be read withl this correction thereintha'tthe same JOHN s. STEWART'.

may conform to( the record ofthe 'case in theI Patent Office.- 'Signedand ysealed this 26th day of June, A. `D. 1914.5.

i (Seal)v Leslie Frazer y Acting commissioner' of Patents.

